A new neuronal marker identified by phosphorylcholine-binding myeloma proteins.

The difficulty of working with the intact brain in vivo has led to the increasing use of nerve cell cultures in neurobiology. However, dissociated cells cannot be unambiguously identified by morphological criteria before the third week in culture, for it is not until then that the basic morphology and size of neurones become stable so that these and other cell types can be easily distinguished. However, cultured neurones can be identified by various cytochemical techniques based on (1) the detection of neurotransmitters or receptors for transmitters, (2) the presence of the Thy 1 antigen and the receptor for tetanus toxin, which are present on the membrane of most neurones, and (3) the presence in neurones of neurone-specific enolase (NSE), a cytoplasmic enzyme, which can only be identified on fixed specimens. Furthermore, other cell types in culture can also be specifically labelled. For instance, antisera to galactocerebroside bind selectively to oligodendrocytes, and antibodies to a neural tumour bind selectively to Schwann cells. We report here the selective interaction of phosphorylcholine-binding myeloma proteins (PC-BMP) with mouse neurones in culture and in suspension. Phosphorylcholine (PC) is found as part of lecithin and sphingomyelin molecules in variable amounts in eukaryotic and prokaryotic membranes, including plasma membranes.     

Hydatellaceae identified as a new branch near the base of the angiosperm phylogenetic tree

Although the relationship of angiosperms to other seed plants remains controversial, great progress has been made in identifying the earliest extant splits in flowering-plant phylogeny, with the discovery that the New Caledonian shrub Amborella trichopoda, the water lilies (Nymphaeales), and the woody Austrobaileyales constitute a basal grade of lines that diverged before the main radiation in the clade. By focusing attention on these ancient lines, this finding has re-written our understanding of angiosperm structural and reproductive biology, physiology, ecology and taxonomy. The discovery of a new basal lineage would lead to further re-evaluation of the initial angiosperm radiation, but would also be unexpected, as nearly all of the approximately 460 flowering-plant families have been surveyed in molecular studies. Here we show that Hydatellaceae, a small family of dwarf aquatics that were formerly interpreted as monocots, are instead a highly modified and previously unrecognized ancient lineage of angiosperms. Molecular phylogenetic analyses of multiple plastid genes and associated noncoding regions from the two genera of Hydatellaceae identify this overlooked family as the sister group of Nymphaeales. This surprising result is further corroborated by evidence from the nuclear gene phytochrome C (PHYC), and by numerous morphological characters. This indicates that water lilies are part of a larger lineage that evolved more extreme and diverse modifications for life in an aquatic habitat than previously recognized.     

浅析钢管开孔补强

主要对常见的等面积补强作了一些分析，使我们清楚地看到补强的范围及面积大小，以便在工作中应用起来，得心应手。     

A new retinoic acid receptor identified from a hepatocellular carcinoma

Processes as diverse as growth, vision and reproduction depend on the presence of vitamin A and its metabolites (retinoids), but the molecular mechanisms which govern these diverse actions remain unclear (for reviews see refs 1,2). A crucial advance recently was the isolation of a specific nuclear receptor for retinoic acid, one of the physiologically active vitamin A derivatives. This nuclear receptor is a member of the steroid/thyroid hormone receptor family. Our analysis of an uncharacterized member of this class of intracellular receptors, encoded by a complementary DNA clone from a human placental library, has led us to discover a second retinoic acid receptor. This new receptor is expressed at high levels in a number of epithelial-type tissues. The gene for the receptor was first identified in a hepatocellular carcinoma where it surrounds a site of integration of hepatitis B virus. Activation by this virus may play a role in tumour development in liver cells, where it is normally not expressed.     

G.729 CS-ACELP语音译码器丢失帧的重建机制

在分组网络中传输语音时,因为存在流量过载的情况,所以需要考虑其引发的分组丢失对生成语音质量的影响,对于采用合成分析法的语音编码方式,一旦分组丢失,会引起译码器输出语音的质量明显降低,介绍了一种于基共轭代数码本激励线性预测编译码器丢失语音帧的重建机制,依照Ｇ．７２９标准的三种兼容程度分别建立模型,重点在于外推出激励信号和综合滤波器参数。运用本机制模拟随机性和突发性的帧丢失两种情况,发现在帧丢失率达３     

缺失数据的估计方法及应用

应用EM算法的思想在双参数逻辑斯蒂克模型下对存在缺失数据的参数估计方法和恢复缺失数据的统计插补方法进行研究.蒙特卡洛模拟和实证研究结果表明,在进行统计插补恢复缺失数据时,该方法使得估计结果比较理想:联合极大似然估计与EM算法相结合,先估计参数,再填补缺失值,再估计,再填补,直到似然函数值稳定.     

Prokaryotic cells of the deep sub-seafloor biosphere identified as living bacteria

Chemical analyses of the pore waters from hundreds of deep ocean sediment cores have over decades provided evidence for ongoing processes that require biological catalysis by prokaryotes. This sub-seafloor activity of microorganisms may influence the surface Earth by changing the chemistry of the ocean and by triggering the emission of methane, with consequences for the marine carbon cycle and even the global climate. Despite the fact that only about 1% of the total marine primary production of organic carbon is available for deep-sea microorganisms, sub-seafloor sediments harbour over half of all prokaryotic cells on Earth. This estimation has been calculated from numerous microscopic cell counts in sediment cores of the Ocean Drilling Program. Because these counts cannot differentiate between dead and alive cells, the population size of living microorganisms is unknown. Here, using ribosomal RNA as a target for the technique known as catalysed reporter deposition-fluorescence in situ hybridization (CARD-FISH), we provide direct quantification of live cells as defined by the presence of ribosomes. We show that a large fraction of the sub-seafloor prokaryotes is alive, even in very old (16 million yr) and deep (> 400 m) sediments. All detectable living cells belong to the Bacteria and have turnover times of 0.25-22 yr, comparable to surface sediments.     

缺失数据下线性模型中缺失值处理方法的比较

在响应变量随机缺失的线性模型中,利用R统计软件模拟比较完全样本法、固定填补法和分数线性回归填补法得到的回归系数、响应变量均值、响应变量的分布函数、响应变量的分位数估计,并用标准误差（SE）评判其优劣.结果表明,除固定填补法外,无论采用其余哪种方法,随着样本容量的增大,评判值SE减小,样本容量越大,估计也就越精确 缺失概率的大小也影响估计的精度,缺失概率越大,相应的评判值SE越大,估计的精度也就越差 另外,在分数线性回归填补法中,J=5的结果总是比J=1的结果好,这说明随着J的增大,其估计精度也随着提高.     

大学体育课堂教学伦理的缺失与建构

本文旨在研究当代大学体育课堂教学伦理的理论建设问题.研究结果表明:大学体育课堂教学伦理的范畴包括外在伦理表征和内在伦理准则两个层面;体育教育功能淡化、师生关系不平等、不分层次教学是当前大学体育课堂教学伦理缺失的三个主要方面;从四种不同伦理需求的角度出发,试图构建一种符合时代伦理精神的大学体育课堂教学伦理道德标准体系.通过理论研究,不仅促使大学体育教师加强对课堂教学实践的伦理学审视,而且有助于引导高校体育健康和谐地发展.     

New mammalian chloride channel identified by expression cloning.

Ion channels selectively permeable to chloride ions regulate cell functions as diverse as excitability and control of cell volume. Using expression cloning techniques, a complementary DNA from an epithelial cell line has been isolated, sequenced and its putative structure examined by site-directed mutagenesis. This cDNA, encoding a 235-amino-acid protein, gave rise to a chloride-selective outward current when expressed in Xenopus oocytes. The expressed, outwardly rectifying chloride current was calcium-insensitive and was blocked by nucleotides applied to the cell surface. Mutation of a putative nucleotide-binding site resulted in loss of nucleotide block but incurred dependence on extracellular calcium concentration. The unusual sequence of this putative channel protein suggests a new class of ion channels not related to other previously cloned chloride channels.     

样本缺失情况下的雷达目标自适应检测

雷达信号自适应检测问题中,参考数据中部分样本丢失会导致常规检测器性能显著下降。在无先验信息条件下,采用期望最大算法获得杂波协方差矩阵的最大似然估计,得到基于期望最大算法的自适应匹配滤波器。利用探测环境的先验信息,在贝叶斯框架下,采用Gibbs抽样获得杂波协方差矩阵的后验均值估计,得到基于马尔科夫链蒙特卡洛自适应匹配滤波器。计算机仿真分析表明,这2种检测器可以在样本缺失情况下具有较好的检测性能。当杂波协方差矩阵先验信息较少时,EM-AMF与MCMC-AMF检测性能相当;当有先验信息可供利用时,MCMC-AMF的检测性能可以得到进一步提升。